The present invention relates to a method and an apparatus comprising a teat cup liner and assembly for milking domestic animals.
Milking machines for domestic animals, such as cows (or goats), generally comprise a teat cup cluster with four (or two) teat cup assemblies connected to a manifold, itself connected to a vacuum source to apply a suction on the animal""s teats. Milk is thereby drawn from the teat, through the manifold into a milk container. Each teat cup assembly has a teat cup shell and inside this an elongate tubular teat cup liner (called an xe2x80x9cinflationxe2x80x9d in the USA) of elastomeric material. The suction from the vacuum source is applied in a pulsating manner to both the inside of the liner, and to a space between the shell and the liner. A differential suction pressure between the inside and outside of the liner within the shell causes this portion of the liner, which is more flexible than adjacent portions, alternately to collapse and open up. When the liner opens up, the teat experiences a greater suction causing milk to flow. When the liner closes, the suction is released, and the liner closes around the end of the teat and presses inwards on the end of the teat. An example of this type of teat cup liner is disclosed in patent document EP 0 124 118.
Certain problems have been noted in use with this type of teat cup liner. Firstly, the liner needs to be heavy enough to stretch the animal""s teat to open milk ducts. The stretching of the teat stresses the teat tissue, the milk ducts, and sphincter valve at the end of the teat. It has hitherto been believed that this stretching is a cause of inflammation of the teat secretory tissues at the base of the animal""s udder, and ultimately mastitis. It has also been thought that the sudden shut off of suction could cause milk to be sucked back into the teat, thereby causing or promoting mastitis. Apart from causing the animal discomfort and pain, these problems can shorten the animal""s effective working life.
One prior art teat cup liner which is concerned with the problem of damage to cows"" teats is GB 2,272,826 A. This document proposes leaving a gap between the point at which the liner collapses and the end of the teat, in order to reduce friction between the end of the teat and the liner when the liner collapses.
Prior art teat cup liners sometimes have a flexible tube to the manifold which doubles back on itself to constrict the passage through the tube when the teat cup cluster is hung in an inverted orientation prior to milking. Another problem that has been noted with such prior art teat cup assemblies is that these often do not reliably shut off flow into the manifold once hung in the inverted orientation. Although in principle, the teat cup assembly could be made heavier to increase the constriction, it is not possible to make the assembly significantly heavier without worsening the problem of mastitis. Therefore, it is necessary for an operator to manually pull down on such liners in order to set the constriction in the flexible tube. This is inconvenient, but if not done, it is possible for airborne bacteria and fungi to enter the manifold and get into the milk.
A related problem is that increasing the weight, or manual pulling of the liner, can cause the liner to begin to tear where it joins to the manifold, usually at the junction between the liner inner bore and connection nipple on the manifold.
Although each of these problems appears to be quite distinct, a change in one part of the teat cup liner, assembly, or cluster to address one problem can make other problems worse. It has therefore proved difficult to make an improved teat cup liner, assembly or cluster.
It is an object of the invention to provide a teat cup liner, a teat cup assembly, a teat cup cluster and a method for milking domestic animals that addresses at least some of these problems.
According to the invention, there is provided an elongate tubular teat cup liner for milking a domestic animal, comprising: an inlet end with an opening into which a animal""s teat may be inserted; an outlet end for discharging milk from the animal; inside the opening a teat engaging portion with annular walls; a collapsible portion adjacent and downstream from the teat engaging portion, the collapsible portion having inner and outer walls being thinner than the walls of the teat engaging portion; an outlet tube leading from the collapsible portion to the outlet end; and a first sealing means and a second sealing means between which lies all of the collapsible portion, the first sealing means being closer to the inlet end than the second sealing means and said first and second sealing means being adapted for making a seal between the outer surface of the liner and a tubular teat cup shell so that a pulsating differential vacuum pressure may be applied to the inner and outer walls of the collapsible portion to cause the collapsible portion to collapse and open repeatedly and so milk the animal, the distance from the opening to a point at which the collapsible portion collapses being sufficient so that the collapsible portion collapses substantially completely away from the animal""s teat, characterised in that the collapsible portion has an elongate cross-section with a minor cross-sectional axis and a major cross-sectional axis, there being a tapering section between the teat engaging portion and the collapsible portion, the tapering portion having outer and inner walls the thickness of which tapers more gradually along a plane encompassing the minor cross-sectional axis than along a plane encompassing the major cross-sectional axis, so that the tapering section may collapse gently on the teat as the collapsible portion collapses.
Surprisingly, it has been found that providing a teat cup liner that does not collapse around the end of the animal""s teat when the differential suction pressure causes the liner to collapse, greatly improves the problems of mastitis, even though the weight of the teat cup assembly or cluster and the speed at which the suction is shut off are essentially unchanged. The teat cup liner according to the invention therefore allows a gap between the end of the teat and the point where the collapsible portion closes to release the suction on the teat. It is thought that this is because any milk that has not yet flowed away from the teat at the time the collapsible portion closes can pool in this gap without being forced back onto the teat.
If the teat cup liner is for milking a cow or a goat, the distance from the opening to the point at which the collapsible portion collapses should be at least about 100 mm so that the collapsible portion collapses substantially completely away from the teat of the cow or the goat.
In the case of the variety of cows most commonly used in milking herds in the United Kingdom, it has been found that an increase in length from the inlet end to the point at which the collapsible portion closes, from approximately 90 mm to approximately 100 mm is sufficient to provide this effect. Goats have teats which when milked are about the same length as the teats of a cow. A person skilled in the art of milking domestic animals, such as goats or cows will be aware the that different animals and different breeds of animals have different sized teats, both in terms of diameter and length. The exact length of the teat cup liner from the inlet end to the point at which the collapsible portion closes can therefore be chosen accordingly.
Preferably, the teat engaging portion is relatively inflexible compared with the collapsible portion, so that the teat engaging portion may collapse gently on the teat as the collapsible portion collapses. The grip between the teat cup assembly and the teat may therefore be maintained as the suction is released on the end of the teat. The gentle collapse helps avoid abrasion of the sensitive tissues at the teat, and also applies a gentle massaging action to the teat between the periods when full suction is applied.
In order to facilitate mass production and improve hygiene in use, the teat cup liner may be a unitary moulding, rather than being formed from separate components.
In order to reduce the potential for damage to the animal""s teat, it is advantageous if the teat cup liner is moulded in a soft elastomeric material, such as a silicone rubber elastomer.
It is particularly advantageous if the elastomeric material is clear or translucent. This allows an operator to make visual inspection of the quantity or quality of milk flowing from a teat, thereby permitting early identification of potential problems in milking performance, including the presence of blood in the milk.
The teat cup assembly will comprise a shell, that may be made from any suitable material, most preferably a clear tough material is such as a polycarbonate plastic. The shell then is fitted to the liner prior to fitting of the liner to the manifold to make up the teat shell cluster. Usually, a separate hose connects to an orifice in the shell to apply suction to the space between the shell and the liner.
In a preferred embodiment of the invention, the first sealing means is an annular rim stretched over a bulbous rim of the teat cup shell. The rim stretches outwardly from the teat cup liner, thereby increasing a positive engagement between the liner and shell at the inlet end of the assembly. Such a positive bond helps keep the liner on the rim if, for example, the assembly is pulled along the ground after the teat cluster has been disconnected from an animal""s udder.
Also in a preferred embodiment of the invention, the second sealing means is a series of at least two spaced annular ribs on the outlet tube, the teat cup shell being seated between an adjacent pair of said ribs. This provides the benefit that the other end of the shell is gripped between the ribs, so preventing movement of the shell at this point either along the length of the liner in either direction.
The outlet tube may have near the outlet end a stiffened support region for connection to a nipple of a manifold inlet of the vacuum source, and adjacent and upstream of the stiffened region a local weakened closure region, so that when the assembly is mounted on the nipple with the support region extending upwardly of the manifold inlet, the weight and length of the assembly being enough to bend the closure region sufficiently to pinch shut closure region. In this respect, the fact that the total length of the assembly may be greater than the length of a prior art assembly, owing to the provision of a gap between the teat and point where the collapsible portion closes, can be used to increase the constriction on the weakened region, due to the increased mechanical advantage from the increased length for a given total weight.
The teat cup assemblies may be connected to a nipple of the manifold inlet. In this case, it is preferred if the nipple is rounded so that the nipple does not cut into the stiffened support region when the closure region is bent to pinch shut the closure region. In particular, this can help to reduce any increased propensity for the nipple to cut into the inner bore of the teat cup liner owing to the increased stresses that could be due to the above-mentioned increase in total length of the liner.
Also according to the invention, there is provided a method of milking a domestic animal using a teat cup assembly as described above, when said teat cup assembly is connected to a vacuum source, in which the method comprises the steps of:
a) inserting a teat of the animal into the inlet end of the teat cup liner;
b) applying a differential vacuum pressure to the inner and outer walls of the collapsible portion to cause the collapsible portion to collapse and open repeatedly and so milk the animal, the collapsible portion being spaced sufficiently from the inlet end so that the collapsible portion collapses substantially completely away from the teat;
characterised in that tapering section has tapering walls that collapse partially to gently compress the end of the animal""s teat.